Central to this proposal for a Nathan Shock Aging Center is a program to develop, maintain, and distribute nutritionally-controlled and pathologically-defined rodent models that are genetically, nutritionally or pharmacologically modified in ways that will allow investigators to test hypotheses concerning aging or age-related diseases. These models will then be examined by Center investigators at the molecular, cellular, and organismic levels to determine whether and how aging is altered. The Animal Core is an integral part of this effort and its overall goal is to maintain, monitor, and distribute new and established animal models for the purpose of testing hypotheses concerning the mechanism(s) underlying aging. The specific aims of the Animal Core are as follows: 1. To establish, maintain, and characterize several new rodent models that can be used to study the mechanisms of aging and/or age-related disease process. Colonies of animals that have been genetically modified or treated with a nutritional and/or pharmacological intervention will be maintained under barrier conditions, and the survival of these colonies will be determined. Animals from these colonies will be made available to Center investigators. 2. To maintain colonies of C57B1/6 mice and Fischer 344 rats under well- defined, barrier conditions and to determine the survival of these colonies. Animals from these colonies will be made available to Center investigator. 3. To coordinate and optimize the distribution of tissues from animals in the Animal Core to faculty at UTHSC-SA and ALMMVH. 4. To assist faculty in maintaining aging colonies of rodents that are supported with funds from independent grants. 5. To advise faculty and students interested in aging on the special requirements of animal husbandry in aging research.